Bacterial cellulose is a broad category of polysaccharides that exhibit highly desirable properties, even though such compounds are essentially of the same chemical structure as celluloses derived from plant material. As the name purports, however, the source of these polysaccharides are bacterial in nature (produced generally by microorganisms of the Acetobacter genus) as the result of fermentation, purification, and recovery thereof. Such bacterial cellulose compounds are comprised of very fine cellulosic fibers having very unique dimensions and aspect ratios (diameters of from about 40 to 100 nm each and lengths of from 0.1 to 15 microns) in bundle form (with a diameter of 0.1 to 0.2 microns on average). Such an entangled bundle structure forms a reticulated network structure that facilitates swelling when in aqueous solution thereby providing excellent three-dimensional networks. The three-dimensional structures effectuate proper and desirable viscosity modification as well as suspension capabilities through building a yield-stress system within a target liquid as well as excellent bulk viscosity. Such a result thus permits highly effective suspension of materials (such as foodstuffs, as one example) that have a propensity to settle over time out of solution, particularly aqueous solutions. Additionally, such bacterial cellulose formulations aid in preventing settling and separation of quick-preparation liquid foodstuffs (i.e., soups, chocolate drinks, yogurt, juices, dairy, cocoas, and the like), albeit with the need to expend relatively high amounts of energy through mixing or heating to initially reach the desired level of suspension for such foodstuffs.
The resultant fibers (and thus bundles) are insoluble in water and, with the capabilities noted above, exhibit polyol- and water-thickening properties. One particular type of bacterial cellulose, microfibrillated cellulose, is normally provided in an uncharged state and exhibits the ability to associate without any added influences. However, without any such extra additives to effectuate thickening or other type of viscosity modification, it has been realized that the resultant systems will themselves exhibit high degrees of instability, particularly over time periods associated with typical shelf life requirements of foodstuffs. As a result, certain co-agents, like carboxymethylcellulose (CMC), also known as cellulose gum, have been introduced to bacterial cellulose products through adsorption to the fibers thereof, following by spray drying (without any co-precipitation steps) in order to provide stabilization and dispersion improvements, most likely through the presence of negative charges on the CMC transferred to the bacterial cellulose fibers themselves. Such charges thus appear to provide repulsion capabilities to prevent the fiber bundles from relaxing the network formed. Even with such a possibility, the selection of a proper CMC has been known to greatly affect the resultant rheological properties of the target bacterial cellulose due to the salt and acid sensitivities of certain CMC products. As such, although improvements in bacterial cellulose utilization have been provided with such CMC inclusions in the past, great care must be taken to ensure the proper level of pH and salt conditions are suitable for the overall formulation. For this reason, further improvements to permit more reliability of bacterial cellulose use in myriad applications are of great interest to the target industries.
Additionally, although such bacterial celluloses are of great interest and importance in providing effective rheological modifications within liquid-based foodstuffs, for the reasons mentioned above, the costs associated with producing such cellulosic materials has proven very high, particularly in terms of necessary labor and waste issues resulting therefrom. Fermentation of such materials initially yields very low amounts. Generally, the production method of purifying and recovering such bacterial cellulose materials entails a cumbersome series of steps after fermentation is complete in order to produce a wet cake with a sufficient amount of bacterial cellulose product in terms of efficiency from initial fermentation. Further spray drying may also affect the final recovery yield of the bacterial cellulose during powder production.
Such excessive steps are not only labor and energy intensive but also result in large amounts of waste water and waste materials that require disposal and handling. As such, the costs for production of bacterial cellulose (in particular microfibrillated cellulose) have proven excessively high relative to other gums, thus restricting the utilization of such a product within certain desirable end-uses. To date, there has been no effective method developed that has remedied these problems, not to mention a method that ultimately provides a bacterial cellulose material that exhibits certain improved properties within target applications as compared with the materials produced through the aforementioned traditional production method.